I have read several ads lately that say that there's something different about a 1970 radio than 71-74. i know the preset buttons are chrome, but I thought that was it. Are the knobs different too? and while i'm on the subject, what do the chrome rings behind the knobs do in a 1 speaker car? one has to be tone, the other?? my car has a 1 speaker dash and somebody put 2 6x9's in the package tray and put in a later model am/fm. the ring that doesnt do tone does something but im not sure what. i cant see how it could be balance if you only have one speaker in the first place?